Most manual and powered staplers include a throat into which a stack of sheets is inserted for stapling. With manual staplers, the user places the stack of sheets into the throat and pushes the actuation arm of the stapler to eject the staple into the stack of sheets. The user typically will have only a rough idea of where the staple will be located with respect to the stack of sheets.
With many electric staplers, the stapling action is triggered when the stack of sheets engages an actuation lever or trips a photosensor somewhere in the throat of the stapler. The user often does not know exactly where the actuation lever or photosensor is, and therefore does not know exactly when the stapling will occur. This makes precise placement of the staple with respect to the stack of sheets difficult.